Friends and colleagues remembered Gabe Zimmerman, the 30-year-old Congressional aide who was shot and killed Saturday in Tucson, Ariz., as a friendly, intellectually curious person whose passion in life was helping others.

Zimmerman, a social worker who was engaged to be married, had been a member of Rep. Gabrielle Giffords’ staff since she first took office in 2007. As Giffords’ director of community outreach, he was “indispensable” and acted as the Congresswoman’s voice in the district, spokesman C.J. Karamargin said.

“He cared deeply about helping people, and that was his reason for being there,” Karamargin said. “He was social worker who was applying his craft in a Member of Congress’ office.”

Zimmerman organized many of Giffords’ public activities, including Saturday’s “Congress on Your Corner” event where the deadly attack took place. Karamargin described his colleague as a model staffer.

“He really loved his job. He really did,” Karamargin said. “It was so important to him to help people, to do what he could to help people. That was his approach.”

Liz Foster, who works at the Arizona Farm Bureau, got to know Zimmerman when he and other Giffords aides met with the Pima County Farm Bureau, which is based in Giffords’ district.

“He was always willing to listen and help where he could,” Foster said. “He would ask lots of questions to try and understand farming and ranching issues. He always put our members at ease.”

As Zimmerman was mourned Sunday, his death served as a reminder that Capitol Hill staffers are as vulnerable as the Members they serve. Speaker John Boehner (R-Ohio) ordered that flags on the House side of the Capitol be flown at half-staff in honor of Zimmerman.

Karamargin said he couldn’t help but be affected by the announcement.

“You know, it was hard to keep it together,” Karamargin said. “I think that is an appropriate act by the Speaker to honor someone who really was through and through a public servant.”

Zimmerman’s death sent shockwaves through the Capitol Hill community. A Facebook page was created in his honor, with several people posting messages.

“The people on my staff — I’m a Republican, she’s a Democrat — but they loved Gabe and really enjoyed working with him, snuffed out at such an early age,” Sen. Jon Kyl (R-Ariz.) said during an appearance on CBS’ “Face the Nation.”

On NBC’s “Meet the Press,” Rep. Ra&uacute;l Grijalva (D-Ariz.) echoed those thoughts, adding that Zimmerman’s mother gave him the first job he ever had in the Tucson community. “This is a shock to all our staffs,” Grijalva said.

Two other Giffords staffers, District Director Ron Barber and aide Pam Simon, were also among those wounded in the attack. Both were given a good prognosis and are expected to recover.

Beyond being a dedicated staffer, Karamargin said Zimmerman was a great friend. The pair traveled to Washington, D.C., for President Barack Obama’s inauguration, he recalled, visiting sites including the Newseum and Lincoln Memorial.

A history lover, Zimmerman wouldn’t leave the memorial until he read all of the Gettysburg Address, Karamargin said.&nbsp; “His intellectual curiosity was just limitless,” he said.

That curiosity was on display just last week, when Zimmerman burst into Karamargin’s office to say he wanted to know more about the Byzantine Empire. “That phrase, ‘I need to know more?’ That was Gabe,” Karamargin said.

Zimmerman’s enthusiasm for life was evident in all areas, Karamargin said. He recalled one recent trip to the gym, where the two did the stair-climber machine side-by-side. “Gabe was drenched, he was just soaked, because ... he threw his all into everything,” he said.

Zimmerman’s friendly nature was evident since he was a teenager. Sommer Mathis went to high school with Zimmerman in Tucson, remembering him as outgoing and popular.

Mathis, news editor at the D.C.-area website TBD.com, last saw Zimmerman a few years ago at a class reunion. After hearing the news of his death Saturday, she looked through photos of him from the reunion, noticing he “seemed really happy.”

“He was a really sweet, kind person, so I’m not surprised to hear he was put in charge of community outreach,” Mathis said. “It seemed like a perfect job for him.”